Gas blast circuit breakers having at least one tubular contact



J. AMALRIC Filed July 18. 1961 May 25, 1965 GAS BLAST cmcurr BREAKERSmvme AT LEAST ONE TUBULAR CONTACT United States Patent 3,185,802 GASBLAST CIRCUIT BREAKERS HAVING AT LEAST ONE TUBULAR CONTACT Jean Amalric,Grenoble, Isere, France, assignor to Etablissements Merlin & Gerin FiledJuly 18, 1961, Ser. No. 124,948 Claims priority, application France,July 18, 1960, 4,274, Patent 1,270,584

4 Claims. (Cl. 200-148) This invention'relates to gas blast circuitbreakers and more particularly to those having at least one tubularcontact.

Amongst the problems encountered in the construction of gas blastcircuit breakers, two are especially important, that is to say, thebreak-down voltage between the contacts in the open position, and theexhaust of the gas blast in such a manner as to assure the maximumefficiency of the extinguishing gas.

The break-down voltage between the contacts is determined by the testingvoltage of the chamber. It 'determines, in its turn, the length oftravel of the movable contact or contacts. Since it is necessary to makethis length as small as possible, met-a1 screens are usually providedwhich surround the contacts in opened position and render the electricheld between them as uniform as possible. In the closed position of thecontacts, these electrodes define an annular space through which the gasblast exhausts at the moment of the separation of the contacts. Thethickness of this annular space plays an important part in the exhaustof the gases, and it is necessary to give it a value which assuresmaximum efficiency in the extinction of the are. It is found that forhigh voltages the break-down distance determined by the testing voltage,and the optimum thickness of the annular space are fairly similar sothat no especial problems are encountered in the choice of theirdimensions. On the other hand for high-voltage circuit breakerscomprisingseveral interrupting chambers, it is necessary, in order tokeep the number of chambers as low as possible, to impose very highdielectric stress on the chambers. As a result it is necessary toprovide break-down distance between the open contacts of as great .alength as is compat ble with the stroke of the movable contact orcontacts. In this case the screens torm an annular space whose thicknessis considerably greater than that necessaryfor a good escape of thegases and an optimum blast efiiciency. It has therefore been necessaryto adopt comprise solutions.

It is an object of the present invention to avoid the necessity for acompromise solution and to make possible the choice of break-downdistances and of annular space dimensions guaranteeing optimum workingconditions.

Other objects and advantages of the invention will become readilyapparent upon reading the following specification in conjunction withthe accompanying drawing.

In this drawing there is schematically shown in axial section an arcextinction chamber of the type which is continually held under pressureand which is actuated according to the invention. In the drawing, 11denotes a body of insulating material constituting the wall of thechamber .11 which is connected through the tube 12 with a compressed airreservoir 13. The upper part of the chamber is closed by a cover 14while the lower part of the chamber is closed by a bell shaped member15. The piston 17 can be moved in a cylinder 16, the latter being solidwith the cover 14. On the cylinder 16 there is mounted a rfixed screen18. The piston 17 is arranged to entrain the first movable contact 19 ata given moment. The movable contact 19 is hollow and opens into a cavity33 closed by a valve 34 which can vent it to atmosphere. A sleeve 20 isfixed on the contact 19 and is actuated by,

on the one hand, a spring 30 which is supported by the piston 17 and, onthe other hand, by the spring 31 which is supported by the cover \14.The first movable contact co-operates with a second movable contact 23,also h0llow, which at its lower end carries a valve 25. This valve isactuated by a piston 26 which slides in a cylinder 27 and on which thespring 28 acts. The contact 23 is provided with an exhaust opening 24near the valve 25. A screen .29 is fixed on the second contact and issimilar to the fixed screen v1-8. The valve 25 is controlled by thepneumatic delay device or relay 37, 38, 39 and 40 through a piston 26.The pneumatic valves 42, 43 can put the interior of the chamber 11' incommunication with the interior of the cylinder 16 by means of the tubes44' and 45, or vent the cylinder 16 to atmosphere. The valve 34 iscontrolled by a pneumatic delay device or relay 46, 47 through a piston36. All these valves and pneumatic relay devices are controlled throughthe tube 48 from a control point.

The circuit breaking device functions as follows:

When the breaker is in the closed position, the contacts 19 and 23 arein theposition indicated in FIGURE 1. When the circuit breaker is in theopen position, the first movable contact is withdrawn so as to beentirely within the screen 18 while the second contact is in theposition shown in the drawing. 'The interior of the chamber 11' which isalways in direct communication with the reservoir v13 is still underpressure. To open the circuit breaker, compressed air is passed into thetube 48. At first this air acts on the piston 36 opening thereby valve34 and on the pistons 42' and 43 of valves 42 and 43 lowering thus saidvalves. The compressed air also penetrates into the cylinder 27, and thepiston 26, at the same time as it raises the Valve .25 from its seat,moves the second contact 23 upwards. The latter moves the first contact19 in the same direction. The interior of the bell shaped member 15 andthe space 33 are vented to atmosphere through the aperture 49. Thevalves 42, 43 have now blocked the tubes 45 and vented to atmosphere theinterior of the cylinder '16. The compressed air in the breaker chambercan now act on the piston 17. If we denote the distance between thescreens 18 and 29 in the closed position of the chamber by a and thestroke effected by the second contact 23 by b, the piston 17 will actupon the sleeve 20 after having effected a stroke of b plus anadditional stroke to compress the spring '30. At this instant, havingacquired a certain velocity, it entnains the contact 19 and causes arapid separation of the two contacts 19 and 23, for the contact 23 hasstopped, being retained by the piston 26. The distance between the twoscreens, at the moment of the separation of the contacts and of theinitiation of the arc is therefore a-b. The two screens, therefore,define at this moment an annular blast space of a thickness a-b throughwhich the compressed air present in the chamber passes into the twohollow contacts, cooling the are under optimum conditions and removingthe ionised gases at first respectively into the bell shaped member 15and the space 33, and then to the atmosphere. After a certain timecorresponding to that necessary for the extinction of the arc, the delaydevices 37, 38, 39, 40 and 46, 47 whose operation will not be describedsince it does not form part of the invention, cut off the supply ofcompressed air coming through the tube 48 and at the same time vent thecylinders 27 and 35 to atmosphere. The piston 26 urged by the spring 28,and in consequence, the second contact 23 return to their initialposition. -It is the same as regards the piston 36 and the valve 34which again close the space 33. The interior of the cylinder 16 is stillvented to atmosphereyand this allows the piston 17 to continue itsstroke until the contact 19 is within the screen '18. The chamber 11'bei g completely closed by the valve 25 and by the valves 42, 43,pressure is rapidly reestablished. The distance between the two screensis again equal to a. To close the contacts, it suffices to put the tubes48 in communication with the atmosphere. The valves 42, 43 return totheir initial position, the compressed air passes through the tubes 45,44 and 45', 44' into the cylinder to, pressure is re-established on thetwo faces of the piston 17 and the spring 31 now entrains the contact 19into its closed position.

It will be realised that the solution according to the invention enablesthe travel b and the distance a to be given values which assure :amaximum efiiciency of blowing while the insulating distance can be giventhe value required by the testing voltage of the chamber.

What is claimed is:

1. A gas blast circuit breaker comprising in combination two alignedrelatively movable elongated contact members, at least one of saidcontact members being tubular, a pair of screen members defining aroundsaid contact members a substantially annular space through which the gasblast exhausts into at least one of said contact members at the momentof their separation, means to bring said screen members nearer to eachother just before the moment of separation of said contact members, andmeans to bring said screen members to their original relative positionafter extinction of the are drawn between said contact members.

2. A gas blast circuit breaker comprising in combination two alignedmovable cylindrical contact members, at least one of said contactmembers having a tubular term, a pair of screen members defining aroundsaid contact members a substantially annular space through which the gasblast is exhausted at the moment of separation of said contact members,one of said screen members being fixed, the other of said screen membersbeing disposed on one of said contact members, said last named contactmember etfecting a reciprocating movement during the opening of thecircuit breaker and urging the other con tact member in the samedirection during its forward movement. 1

3. A gas blast circuit breaker comprising in combination two alignedmovable cylindrical contact members, at least one of said contactmembers having a tubular form, a pair of screen members defining aroundsaid contact members a substantially annular space through which the gasblast is exhausted at the moment of separation of said contact members,one of said screen members being fixed, the other of said screen membersbeing disposed on one of said contact members, said last named contactmember effecting a reciprocating movement during the opening of thecircuit breaker, and an exhaust valve rigidly connected to said lastnamed contact member.

4. A gas blast circuit breaker comprising in combination two alignedrelatively movable tubular contact members, a pair of screen membersdefining around said contact members a substantially annular spacethrough which the gas blast exhausts into said contact members at themoment of their separation, means to bring said screen members nearer toeach other during the beginning of the blast period, and means to bringsaid screen members to their original relative position at the end ofsaid blast period.

References Cited by the Examiner UNITED STATES PATENTS 3,027,439 3/62Upton et al. 200148 FOREIGN PATENTS 432,453 7/35 Great Britain. 575,8873/ 46 Great Britain.

BERNARD A. GILHEANY, Primary Examiner,

1. A GAS BLAST CIRCUIT BREAKER COMPRISING IN COMBINATION TWO ALIGNEDRELATIVELY MOVABLE ELONGATED CONTACT MEMBERS, AT LEAST ONE OF SAIDCONTACT MEMBERS BEING TUBULAR, A PAIR OF SCREEN MEMBERS DEFINING AROUNDSAID CONTACT MEMBERS A SUBSTANTIALLY ANNULAR SPACE THROUGH WHICH THE GASBLAST EXHAUSTS INTO AT LEAST ONE OF SAID CONTACT MEMBERS AT THE MOMENTOF THEIR SEPARATION, MEANS TO BRING SAID SCREEN MEMBERS NEARER TO EACHOTHER JUST BEFORE THE MOMENT OF SEPARATION OF SAID CONTACT MEMBERS, ANDMEANS TO BRING SAID SCREEN MEMBERS TO THEIR ORIGINAL RELATIVE POSITIONAFTER EXTINCTION OF THE ARC DRAWN BETWEEN SAID CONTACT MEMBERS.